BIOD 171 Essential Microbiology Final Exam 2026/2027 UPDATE
1. Who is credited with first observing living microorganisms using a high-
quality magnifying lens?
A. Robert Hooke
B. Antonie van Leeuwenhoek
C. Louis Pasteur
D. Robert Koch
Answer: B
Rationale: Antonie van Leeuwenhoek is known as the Father of Microbiology for being the
first to observe ‘animalcules’ (bacteria and protozoa) using his handcrafted microscopes.
2. Which of Koch’s Postulates involves the re-isolation of the microbe from a
newly diseased experimental host?
A. Postulate 1
B. Postulate 4
C. Postulate 3
D. Postulate 2
Answer: B
Rationale: Postulate 4 states that the same microorganism must be re-isolated from the
inoculated, diseased experimental host and identified as being identical to the original
specific causative agent.
,3. In the Gram stain procedure, what is the function of iodine?
A. Primary stain
B. Counterstain
C. Mordant
D. Decolorizer
Answer: C
Rationale: Iodine acts as a mordant, forming a complex with the crystal violet dye that gets
trapped in the thick peptidoglycan layer of Gram-positive cells.
4. A bacterium with a ‘peritrichous’ flagellar arrangement has:
A. A single flagellum at one end
B. A tuft of flagella at one end
C. One flagellum at each end
D. Flagella covering the entire surface
Answer: D
Rationale: Peritrichous refers to flagella distributed over the entire surface of the bacterial
cell.
5. Which bacterial structure is primarily responsible for preventing phagocytosis
by host immune cells?
A. Plasma membrane
B. Ribosome
C. Capsule
D. Plasmid
Answer: C
Rationale: The capsule is a glycocalyx layer that is organized and firmly attached to the cell
wall, providing protection against phagocytosis.
, 6. Which of the following is found in the cell wall of Gram-negative bacteria but
NOT in Gram-positive bacteria?
A. Peptidoglycan
B. Teichoic acids
C. Lipopolysaccharide (LPS)
D. N-acetylglucosamine
Answer: C
Rationale: Lipopolysaccharide (LPS) is a major component of the outer membrane in
Gram-negative bacteria; it contains Lipid A, which acts as an endotoxin.
7. Which organelle in eukaryotic cells is responsible for the synthesis of lipids
and detoxification of chemicals?
A. Smooth Endoplasmic Reticulum
B. Rough Endoplasmic Reticulum
C. Golgi Complex
D. Lysosome
Answer: A
Rationale: The Smooth ER is involved in lipid synthesis, calcium storage, and the
detoxification of harmful metabolic byproducts or drugs.
8. What is the net gain of ATP molecules produced during glycolysis from one
molecule of glucose?
A. 2 ATP
B. 4 ATP
C. 34 ATP
D. 38 ATP
Answer: A
Rationale: While 4 ATP are produced in total during the payoff phase of glycolysis, 2 ATP
are consumed in the preparatory phase, resulting in a net gain of 2 ATP.
1. Who is credited with first observing living microorganisms using a high-
quality magnifying lens?
A. Robert Hooke
B. Antonie van Leeuwenhoek
C. Louis Pasteur
D. Robert Koch
Answer: B
Rationale: Antonie van Leeuwenhoek is known as the Father of Microbiology for being the
first to observe ‘animalcules’ (bacteria and protozoa) using his handcrafted microscopes.
2. Which of Koch’s Postulates involves the re-isolation of the microbe from a
newly diseased experimental host?
A. Postulate 1
B. Postulate 4
C. Postulate 3
D. Postulate 2
Answer: B
Rationale: Postulate 4 states that the same microorganism must be re-isolated from the
inoculated, diseased experimental host and identified as being identical to the original
specific causative agent.
,3. In the Gram stain procedure, what is the function of iodine?
A. Primary stain
B. Counterstain
C. Mordant
D. Decolorizer
Answer: C
Rationale: Iodine acts as a mordant, forming a complex with the crystal violet dye that gets
trapped in the thick peptidoglycan layer of Gram-positive cells.
4. A bacterium with a ‘peritrichous’ flagellar arrangement has:
A. A single flagellum at one end
B. A tuft of flagella at one end
C. One flagellum at each end
D. Flagella covering the entire surface
Answer: D
Rationale: Peritrichous refers to flagella distributed over the entire surface of the bacterial
cell.
5. Which bacterial structure is primarily responsible for preventing phagocytosis
by host immune cells?
A. Plasma membrane
B. Ribosome
C. Capsule
D. Plasmid
Answer: C
Rationale: The capsule is a glycocalyx layer that is organized and firmly attached to the cell
wall, providing protection against phagocytosis.
, 6. Which of the following is found in the cell wall of Gram-negative bacteria but
NOT in Gram-positive bacteria?
A. Peptidoglycan
B. Teichoic acids
C. Lipopolysaccharide (LPS)
D. N-acetylglucosamine
Answer: C
Rationale: Lipopolysaccharide (LPS) is a major component of the outer membrane in
Gram-negative bacteria; it contains Lipid A, which acts as an endotoxin.
7. Which organelle in eukaryotic cells is responsible for the synthesis of lipids
and detoxification of chemicals?
A. Smooth Endoplasmic Reticulum
B. Rough Endoplasmic Reticulum
C. Golgi Complex
D. Lysosome
Answer: A
Rationale: The Smooth ER is involved in lipid synthesis, calcium storage, and the
detoxification of harmful metabolic byproducts or drugs.
8. What is the net gain of ATP molecules produced during glycolysis from one
molecule of glucose?
A. 2 ATP
B. 4 ATP
C. 34 ATP
D. 38 ATP
Answer: A
Rationale: While 4 ATP are produced in total during the payoff phase of glycolysis, 2 ATP
are consumed in the preparatory phase, resulting in a net gain of 2 ATP.
